Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$214.94	6.322%	$228.5285	$228.53	$228.55	$228.50
Purchase #2	$192.70	8.728%	$209.5189	$209.52	$209.50	$209.50
Purchase #3	$150.64	3.266%	$155.5599	$155.56	$155.55	$155.60
Purchase #4	$132.29	9.511%	$144.8721	$144.87	$144.85	$144.90
Purchase #5	$109.54	13.622%	$124.4615	$124.46	$124.45	$124.50
Purchase #6	$200.89	6.500%	$213.9479	$213.95	$213.95	$213.90
Purchase #7	$83.53	7.375%	$89.6903	$89.69	$89.70	$89.70
7 purchase totals =	$1,084.53		$1,166.5791	$1,166.58	$1,166.55	$1,166.60